Device and a method for optional closing of a section of a well

ABSTRACT

A device and method for optional closing of a section of a well formation ( 6 ) in which there is disposed a pipe ( 2 ), and where the pipe ( 2 ) is provided with at least two receivers ( 1 ) or pluggable openings ( 28 ), with receivers ( 1 ) or pluggable openings ( 28 ) in different sections of the well formation ( 6 ) having different dimensions and/or geometry, whereby the receivers ( 1 ) and the pluggable openings ( 28 ) are arranged so as allow optional closing of these through supplying the pipe ( 2 ) with a sealing body ( 4, 32 ) of a corresponding dimension and/or geometry.

This invention regards a device for optional shut-off of the inflow froma section of a well. More specifically, it regards a device in whichbodies having a specific geometry and dimension are placed incorresponding openings in a section of a well in order to be able toclose the section permanently or for a period of time. The inventionalso includes a method of implementing the invention.

A well such as petroleum well is often lined with a casing, where thesection of casing running through the well formation is perforated inorder to allow the inflow of formation fluid. Due to the geologicalcharacteristics of the well formation and the extent of the well inquestion, and its positioning in the well formation, it may be desirableto close one or more sections of the well for a longer or shorter periodof time. The aim may be to stimulate the inflow of well fluid from theother well sections or reduce the inflow or water or gas.

It is known to use surface operated inflow control valves. These arecostly and often have a low operational reliability.

It is also known to lead bodies to a well section in order to plugperforations to stop inflow from the well through the perforations. Thusthe publication GB 2167472A concerns a method of arranging sphericalsealing bodies in perforations in the casing of a deviated well. Themethod entails placing the sealing bodies in perforations on the insideof the casing. The method is not suitable for shutting down fluidproduction, as the balls will fall out of the perforations whensubjected to flow through the perforations in the opposite direction.The method is intended to limit fluid inflow into the formation, e.g. inthe case of stimulation operations.

The object of the invention is to remedy the disadvantages of prior art.

The object is achieved in accordance with the invention by thecharacteristics stated in the description below and in the followingclaims.

In a tubular passage, hereinafter termed production tubing, there isdisposed at least one receiver having a through opening in which thereceiver is designed to sealingly capture and hold a sealing body thatexhibits a geometry and dimension that correspond to that of theopening, the sealing body being preferably carried from the surface in acarrier fluid.

The receiver may, as an example, be disposed between well sections.Using several receivers in a well where each receiver is designed to beable only to capture a sealing body with a corresponding geometry anddimension, makes it possible to select which section of the well is tobe closed.

If the well is to be closed, e.g. at the second receiver, counting fromthe surface, a sealing body is selected which can pass through the firstreceiver, and which is a complementary fit to the second receiver.

A receiver according to the invention is equipped with a barrierdesigned to prevent dislocation of the captured sealing body from thereceiver after production from the well has been initiated.

In an alternative embodiment at least one flow chamber is providedbetween the well formation and the production tubing. The flow chambercommunicates with the well formation via at least one chamber opening,possibly via a sand screen and/or other fluid flow-through devices. Theflow chamber communicates with the production tubing via at least onepluggable opening and possibly via other fluid flow-through devices.

Through the construction of the pluggable opening, the flow chamber isdesigned only to be able to receive sealing bodies that have been givengeometry and dimension corresponding to that of the pluggable opening,and also smaller sealing bodies. Other sealing bodies will not be ableto pass into the flow chamber. Moreover, the shape of the pluggableopening may be such as to allow sealing bodies of a specific dimensionor a specific dimensional range to only flow into the flow chamber, andnot back through the pluggable opening.

By means of a sealing body flowing onwards, settling over and closingthe chamber opening, any further inflow of sealing bodies and carrierfluid through the pluggable opening and into the flow chamber isprevented.

When sealing bodies are caused to flow into the production tubing fromthe surface, sealing bodies of a suitable geometry and a dimensionsmaller than or equal to that of the pluggable opening flow into theflow chamber. Sealing bodies that are unable to pass through thepluggable opening will be able to settle over and close the pluggableopening.

By providing flow chambers in different sections of the well withpluggable opening of different dimension and possibly is differentgeometry, it becomes possible, by introducing a specific type of sealingbodies into the well, to decide which flow chamber(s) sealing bodies areto be fed to.

When the inflow of sealing bodies to the well is stopped and well fluidis subsequently allowed to flow from the well formation and into theproduction tubing via the flow chamber, sealing bodies of a smallerdimension may flow back to the production tubing via the pluggableopening, while other sealing bodies located in the flow chamber remainand are able to plug the pluggable opening, thus preventing well fluidfrom flowing into the production tubing.

The sealing bodies may be made from a material, which dissolves overtime as a result of e.g. corrosion or other chemical or thermaldecomposition. It may be possible to dissolve the sealing bodies by useof certain fluids such as acids or bases, or they may be of a permanenttype. Time-limited closure may be of interest e.g. when conducting teststo determine which flow chambers are to be closed.

The device is equally well suited for both lined and unlined wells.

The following describes a non-limiting example of a preferred embodimentand method illustrated in the accompanying drawings, in which:

FIG. 1 shows production tubing disposed in a well formation, whichproduction tubing is equipped with two receivers, and where a sealingbody is passing into the well;

FIG. 2 shows the same as FIG. 1, but here the sealing body has beencaptured in a receiver;

FIG. 3 shows production tubing equipped with two flow chambers andarranged in a well formation;

FIG. 4 shows the device of FIG. 3 on a larger scale, where a sealingbody is entering the flow chamber;

FIG. 5 shows a sealing body that is too large to pass into the flowchamber; and

FIG. 6 shows a sealing body that is too large to pass out of the firstopening of the flow chamber.

In the drawings, reference number 1 denotes a receiver that is placed inproduction tubing 2, and which is designed to capture a sealing body 4of a corresponding geometry and dimension. The production tubing islocated in a well formation 6, where sections of the well formation 6can be separated by a packing 8 that has been set in the annulus 10between the production tubing 2 and the well formation 6. The receiver 1is formed with a shoulder 12 designed to prevent sealing bodies 4 with acorresponding geometry and dimension to that of the receiver 1 frompassing through the receiver 1.

Advantageously, several receivers 1 are arranged along the productiontubing 2 in a well formation. The receivers 1 are shaped so as to have aflow dimension, which decreases away from the surface, with the receiver1 located closest to the surface having the largest flow dimension, andthe receiver 1 located furthest away having the smallest flow dimension.

The receiver 1 is equipped with a barrier 14, which may be in the formof e.g. a flexible material or a spring mechanism of a type that isknown per se. The barrier 14 is formed so as to allow a sealing bodyhaving a geometry and dimension corresponding to that of the receiver 1in question to be moved through the barrier 14 in one direction, but notin the opposite direction. Smaller sealing bodies may pass through thebarrier in both directions.

By passing a sealing body of a specific geometry and dimension into thewell, it is possible to select which receiver is to be closed, see FIGS.1 and 2.

When well fluid flows into the production tubing 2 the barrier 14prevents the sealing body 4 from flowing back to the surface.Consequently, the receiver 1, the sealing body 4 and the barrier 14 willtogether form a sealing device in the production tubing 2.

In an alternative embodiment at least one flow chamber 20 is sealinglyconnected to the production tubing 2 and placed in the well formation 6,see FIG. 3. The sections of the well formation 6 may, as describedabove, be separated by a packing 8 that has been set in the annulus 10between the production tubing 2 and the well formation 6.

The wall portion 22 of the flow chamber 20 is provided with a chamberopening 24 arranged to connect the cavity 26 of the flow chamber 20 withthe well formation 6. A pluggable is opening 28 runs through the wall 30of the production tubing 2, and is arranged to connect the cavity 26with the production tubing 2.

By equipping a flow chamber 20 or groups of flow chambers 20 with apluggable opening 28 of different geometry or dimensions, it becomespossible to select which flow chamber or flow chambers 20 is/are to beclosed by supplying the flow chamber 20 in question with sealing bodiesof a corresponding geometry and dimension.

The chamber opening 24 is dimensioned so that sealing bodies 32 of thedimension in question cannot pass through the chamber opening 24.

The pluggable opening 28 is equipped with a back flow stopper 34, wherethis may be constructed from a flexible material or as a springmechanism that is known per se.

When a sealing body 32, here in the form of a ball, passes through theproduction tubing 2 together with a carrier fluid, the ball 32 will seekto follow the fluid out of the production tubing 2 via the pluggableopening 28, the cavity 26 and the chamber opening 24, to the wellformation 6.

Balls 32 smaller than the diameter of the pluggable opening 28 will beable to flow in through the pluggable opening 28 and the back flowstopper 34 to the cavity 26, see FIG. 4, while larger balls 32 will beunable to enter the pluggable opening 28, see FIG. 5.

Upon flow from the cavity 26 to the production tubing 2, smaller balls32 may pass back through the back flow stopper 34 and the pluggableopening 28. Balls 32 of a size that allows them into the cavity 26through the pluggable opening 28 and the back flow stopper 34 will, dueto the construction of the back flow stopper 34, upon return be stoppedby the back flow stopper 34, thus sealing the pluggable opening 28, seeFIG. 6.

Balls 32 present in the cavity 26 may during the inflow of carrier fluidfrom the production tubing 2 settle sealingly over the chamber opening24, thus preventing further inflow of carrier fluid to the cavity 26.

By using dissolving sealing bodies 4, 32 the closing function of thesealing bodies 4, 32 may be timed or controlled through injection ofliquid solvents. Thus the device of the invention makes it possible tocontrol, which receivers 1 or flow chambers 20 are to be closed, andalso how long they are to remain closed.

1. A device for optional closing of a section of a well formation (6) inwhich there is disposed a pipe (2), characterized in that the pipe (2)is provided with at least two receivers (1) or pluggable openings (28),with receivers (1) or pluggable openings (28) in different sections ofthe well formation (6) having different dimensions and/or geometry,whereby the receivers (1) and the pluggable openings (28) are arrangedso as allow optional closing of these through supplying the pipe (2)with a sealing body (4, 32) of a corresponding dimension and/orgeometry.
 2. A device in accordance with claim 1, characterized in thatthe receiver (1) is provided with a barrier (14) arranged to prevent asealing body (4) that corresponds to the receiver (1) from beingdisplaced out of the receiver (1).
 3. A device in accordance with claim1, characterized in that a flow chamber (20) is arranged sealinglybetween the pipe (2) and the well formation (6), where the flow chamber(20) is communicatingly connected to the well formation (6) by means ofa chamber opening (24) and to the pipe (2) by means of a pluggableopening (28), the flow chamber (20) being arranged to receive at leastone sealing body (32), where the sealing body (32) is arranged to sealthe chamber opening (24) and/or the pluggable opening (28).
 4. A devicein accordance with claim 2, characterized in that the pluggable opening(28) is equipped with a back flow stopper (34) arranged to allow thepassage of a corresponding sealing body (32) in one direction but not inthe opposite direction.
 5. A device in accordance with one or more ofthe preceding claims, characterized in that the sealing body (32) ismade from a dissolving material.
 6. A method of optional closing of asection of a well formation (6) in which there is arranged a pipe (2),and which in addition is provided with a device in accordance with oneor more of the preceding claims, characterized in that a sealing body(4, 32) of a dimension and/or geometry that corresponds to the barrier(14) or the pluggable opening (28) to be closed, is brought into thepipe (2).